The present invention relates to subterranean treatments and, more particularly, in one or more embodiments, to introducing a hydrophobically and cationically modified relative permeability modifier into a subterranean interval to reduce the effective permeability of the subterranean interval to aqueous-based fluids.
The production of water with hydrocarbons, oil and/or gas, from wells constitutes a major problem and expense in the production of the hydrocarbons. While hydrocarbon producing wells are usually completed in hydrocarbon producing formations, the formations frequently contain layers of water or may be located adjacent to water producing zones. The high mobility of the water often allows it to flow into the wellbore by way of natural fractures and/or high permeability streaks present in the formation. Over the life of such wells, the ratio of water to hydrocarbons recovered often becomes so high that the cost of producing the water, separating it from the hydrocarbons and disposing of it represents a significant economic loss.
Chemicals referred to as relative permeability modifiers have been utilized to decrease the production of water with hydrocarbons. That is, water permeability modifying chemicals such as polyacrylamide have been introduced into hydrocarbon and water producing formations so that the chemicals attach to adsorption sites on surfaces within the porosity of the formations. The presence of the chemicals in the formations has the effect of reducing the flow of water through the formations. The use of water permeability modifying chemicals in hydrocarbon and water producing formations to decrease the production of water involves less risk than other techniques such as blocking the flow of water with cross-linked polymers, and has the advantage that they do not require expensive zonal isolation techniques. However, the use of hydrophilic water permeability modifying chemicals, e.g., polyacrylamides, have heretofore resulted in only small temporary reductions in water production and/or unacceptable levels of reduction in hydrocarbon production.
Hydrophobically modified polymers have recently been used as relative permeability modifiers. Hydrophobically modified polymers may also be used in operations to assist in leak off control, clay stabilization, fines control, cement fluid loss control, and the diversion of treatment fluids. However, under certain pH and temperature conditions (e.g., at temperatures above 140° F. and at pH's above 7) these polymers may precipitate out of solution limiting their effectiveness as relative permeability modifiers.
Thus, improvements are necessary in the methods and compositions used to reduce water permeability in water and hydrocarbon producing subterranean formations. Additionally, improved formation stimulation methods capable of stimulating production while also reducing the production of water from a formation with temperatures above 140° F. and/or while using treatment fluids that have pH's above 7 are necessary.